Seems like the author satirically argues against Objectivism by putting up lack of charity and generosity as a straw man characterization to attack. He completely ignores the fact that taxation is collected irrespective of goodwill attitude, and under the threat of force (violence/jail).

I frankly would have hoped the argument was not a straw man and that he argued against the actual essence of the philosophy of Objectivism. Instead of taking the cheap way out to argue against a mere peripheral unfortunate potential consequence of it (when taken to an extreme).